Coil form for a magnetic deflection york

ABSTRACT

A magnetic deflection yoke has internal longitudinal slots and two end caps. Each of the end caps has hook members to allow a deflection yoke to be wound with each wire in each coil being precisely positioned to reduce deflection distortion. The core may be cylindrical or tapered in shape. A flattened trumpetshaped wire feeder is used for feeding wire under tension between the end caps and hooking the wire behind them.

Inventors Appl. No.

Filed Patented Assignee United States Patent William R. Cll'istiana Saugertios;

Joseph F. Hevd, I-Iurley, both or, N.Y. 7,275

Jan. 30, 1970 Aug. 24, 197 1 International Business Machines Corporation Armonk, N.Y.

COIL FORM FOR A MAGNETIC DEFLECTION YORK 9 Claims, 9 Drawing Fig.

US. Cl 335/210, 335/213 Int. Cl H01! 7/00 Field of Search 335/210,

[56] References Cited UNITED STATES PATENTS 3,310,763 3/1967 Thompson 335/213 3,430,169 2/1969 Gabor 335/213 Primary Examiner-G. Harris Altorneys- Hanifin and Jancin and George E. Clark ABSTRACT: A magnetic deflection yoke has internal longitudinal slots and two end caps. Each of the end caps has hook members to allow a deflection yoke to be wound with each wire in each coil being precisely positioned to reduce deflection distortion. The core may be cylindrical or tapered in shape. A flattened trumpet-shaped wire feeder is used for feeding wire under tension between the end caps and hooking the wire behind them.

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COIL FORM FOR A MAGNETIC DEFLECTION YORK BACKGROUND OF THE INVENTION The present invention relates to precision coil structures and methods for winding such structures and, in particular, to an improved configuration for deflection coils in magnetic deflection yokes and a method for winding a precisely defined magnetic deflection yoke.

Deflection coils for electron beams normally include longitudinal portions, radial portions, and transverse portions. The longitudinal portions are generally along the axis of the electron beam device such as a cathode-ray tube. Current through the longitudinal portions produces a component of magnetic field that is transverse to the axis of the beam which causes a deflection of the beam. Current flowing through the radial portions and the transverse portions of deflection coils produce components of magnetic field axially directed which tends to defocus the electron beam.

A usual production technique in the manufacture of magnetic deflection yokes is to wind the coils on a bobbin device separate from the yoke core and then'fit the coils onto the core. As a result, it is difficult or impossible to achieve precision or predictability-as to placement or distribution of either the longitudinal portions, the radial portions or the transverse portions of each coil or group of coils. Hence, such magnetic deflection yokes do not have predictable magnetic field patterns.

Imprecision in the deflection coils results in various distortionswhen an image is displayed on the face of a cathode-ray tube. One is the defocusing of the spot and changes in its shape at positions away from the center of the CRT, and another is the lack of perpendicularity between the x and y components due to the imprecise placement of the x and y deflection coils with respect to each other.

Prior art attempts to correct the distortions due to imprecise placement and distribution of deflection coils have included very high cost methods requiring manual winding and forming of deflection coils.

Accordingly, it is an object of the present invention to wind deflection coils which will produce predictable magnetic fields.

A further object is to wind deflection coils on an internally slotted core structure with end caps arranged to achieve a high degree of repeatability among a large number of coils produced.

A still further object of the present invention is to reduce.

defocusing and distortion due to end effects of the magnetic deflection coils.

Other objects of the invention are to provide, in an improved deflection yoke as aforesaid, a core structure on which the coils are wound in their final position; and which provides desired lineal response in the operation of the yoke.

Another object of the present invention is to provide a lowcost magnetic deflection yoke which will produce a predictable magnetic field for deflecting an electron beam.

SUMMARY The instant invention'is embodied in a magnetic deflection yoke including a plurality of deflection coils and in a method for making a magnetic deflection yoke. A deflection yoke, in which deflection coils are precisely placed in slots in the core and held in precise position by a numberof hook members affixed at either end of the core, is wound as follows:

i. Thecore with end caps affixed is mounted on a winding 2. A wire is fed under tension along one of the slots in the core;

3. The wire under tension is then hooked around an end cap at the end of the core;

4. The core is then rotated through angle 8;

5. The wire is fed under tension axially along another slot to the opposite end of the core;

6. The wire is then hooked around a hook member on the other end cap; 7. The core is later rotated through an angle 26; and 8. The steps are repeated through slots flanking the first pair, and so on. g I v The hook members on the end caps define annular channels which'place and maintain the end turns of the coils in tight transverse bundles positioned to minimize interference with the useful components of the operating fields of the yoke.

These and other objects and advantages of the invention will be explained in further detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS represents one preferred embodiment of the instantinvention.

FIGS. 2 and 3 are detail views of the front and rear end cap structures of the yoke of FIG. 1.

FIG. '4 shows apparatus for winding deflection coils for a magnetic deflection yoke according to the instant invention.

FIGS. 5A and 5B show enlarged front and side views of the wire-feeding tool of FIG. 4, used to feed wire around the end caps of the deflection yoke.

FIG. 6A shows the shape of a single turn of a deflection coil wound according to the present invention.

FIG. 6B shows a multiple turn section of a deflection coil wound according to the present invention.

FIG. 7 is a cross section view of a cylindrical-shaped magnetic deflection yoke according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, a magnetic deflection yoke with a tapered core is shown as one embodiment of the present invention.

Yoke includes a core structure which isflared outwardly towards the front, and includes al ferromagnetic body and slotted'end caps and 130. windings 50 are shown in phantom to reveal the core structure details. End cap 120 includes hook members 124, and an extension 126 which forms a core liner having longitudinal slots 122. Rear end cap 130 abuts with extension 126 and body 110 and is positioned so that the slots in extension 126 are in alignment with the slots in rear end cap 130. Rear end cap 130 includes hook members 134 for holding the windings 50 precisely in position. Each of the arrays of hooks 120 and 130 defines an annular channel 136, 138 for receiving the end turns of coils 50.

Referring now to FIG. 3, a cross section of rear end cap 130 is shown. End caps 120 and 130 are formed of phenolic or hard plastic material. The extended slots in end cap I20 are aligned with the slot formed between hook members 134 in end cap 130 and cemented in place. The hook members 124 on end cap 120 and 134 on end cap 130 enable precise positioning of each turn of each coil in a magnetic deflection yoke.

Referring now to FIG. 7, an alternate embodiment of the present invention is shown in which the yoke 140 is cylindrical in shape. In this embodiment, the end caps 142, 143 are identical and the windings 148 lie in a plane parallel to the undeflected direction of. electron beam in slots formed in the ferromagnetic core body.

The embodiment of FIG. 7 also illustrates an alternative composition of the core wherein the core is composed-of interleaved sections 145 of magnetic materials with sections 146 of nonmagnetic material to modify the magnetic flux pattern produced by the deflection yoke. The nonmagnetic sections 146 are slotted as well as the magnetic sections 145 of the core and these slots must be aligned with each other and with the slots in end caps 142 and 143 to allow precise positioning of the deflection coils. It will be understood the embodiments of FIGS. 1 and 7 are given as examples, and that either could be constructed with features, such as the composite core or the plastic liner, of the other. Moreover, the core structure could be of the air core kind, in which the entire tooth, slot and liner assembly is nonmagnetic.

Referring now to FIG. 4, a fixture is shown which may be used to automatically wind deflection coils on a yoke frame such as shown in FIGS. 1 and 7.

Yoke 100 is mounted on fixture 290. The yoke is rotatable by motor 280, which is mounted on slides 255 hung from baseplate 250.

Wire 205 is fed from spool 210 through guide 220 to slidehead 230 carrying a tool 240' which has a hole drilled through it to allow the wire to pass. Slidehead 230 is reciprocally mounted on track 232 and connected to driving rod 236 by coupler 234. Driving rod 236 imparts linear motion to slidehead 230 along track 232 to cause feeding head 300 of tool 240 to move along the axis of the yoke. Motor 280 is connected to fixture 290 by shaft 281 which passes through a slot 251 in plate 250. Means not shown cause the motor 280 to move along slides 255 in the z axis perpendicular to the page to move yoke 100 in order to allow feeding head 300 to clear hook members 134 on rear end cap 130 and hook members 124 on end cap 120.

Referring now to FIGS. 5A and 5B, feeding toolhead 300 is shown with trumpet-shaped end 310 which enables reversing the direction of the wires around the end caps of the core assembly, and trough 320 which guides the wire during the winding ofa deflection coil. The wire is fed through slot 315 at the rear of the feeding tool 300 and out through hole 316 to trough 320.

Referring again to FIG. 7, a cylindrical yoke embodiment of the present invention is shown mounted on the neck 150 of a CRT. The trumpetor flare-shaped yoke 100 mounts on a CRT in the same manner as the cylindrical yoke 140. However, the flared yoke 100 is capable of being positioned further up on the bell 151 of the CRT.

OPERATION Referring now to FIGS. 2 and 4, the method of winding deflection coils to precisely position each turn of each coil and reduce distortionwill be described.

Feeding tool 300 feeds wire 205 under tension from a terminal (not shown) along a slot formed by end cap 120. For example, the first wire might be placed in slot 2. Feeding tool 300 proceeds beyond the lower end cap 130 to clear the teeth and any wire bundle previously built up in the trough 138. The fixture 290 is then displaced in the z axis to allow the feeding tool to clear hook members 134 radially, and then theprobe is retracted slightly to place the feedhead in line with annular trough 138. Motor 280 then indexes yoke 100 through an angle 8 which aligns feeding tool with another of the slots, for example, slot f. Feeding tool 300 hooks the wire under tension around the hook member 134 in the lower end cap and the tool 300 is again lowered to clear the teeth. The fixture is then displaced along the z axis to align the feeding tool with the yoke axis again. The feeding tool 300 is then withdrawn drawing the wire under tension along slot f until the tool is clear of the upper end cap 120. The fixture is then displaced in the z and vertical axes to allow the feeding tool 300 to clear the hook members 124 in the upper end cap 120 analogously to the aforedescribed hooking motions. Motor 280 again indexes the yoke 100 through an angle 8 and a second turn is wound in slots 2 and f. After a specified number of turns are wound in slots e and f, the yoke is indexed through angle 8+8 and the wire is then fed downwardly under tension along slot d.

When feeding tool 300 is clear of the end cap 130, fixture 290 is displaced along the vertical and z axes as before to allow the feeding tool to clear the hook members 134 on end cap 130. Motor 280 rotates the yoke through an angle 36 causing the wire under tension to be fed behind the hooks of the end cap to the next slot, in the example, slot g. The wire is then fed under upwardly tension along slot g to the upper end of the yoke-clear of end cap 120, and the fixture is rotated by motor 280 back through the angle 38 to slot d.

The process of winding is continued with successive turns of wire-being fed along the slots d and g, and then additionally flanking slot pairs e and h and b and j, the fixture and tool being moved as described above to complete one multisection coil. In a magnetic deflection yokethere are normally such four coils. Two coils deflect the electron beam in the positive and negative vertical direction from a center point and two coils deflect the electron beam in the horizontal direction from the same center point. t

In the winding apparatus shown in FIG. 4, each of the coils is wound in sequence nd the wire ends are brought to terminals (not shown) for connection to the deflection circuitry. In the example given, each coil covers nearly 180, and so the vertical and horizontal coils will overlap in the annular channels 136, 138. If desired, the hook members 120, can be provided with secondary toothlike projections (not shown) dividing the channels 136, 138 into subchannels to separate the end turns of the vertical and horizontal coils.

Although the method shown has been described in relation to a particular winding apparatus, the inventive method is equally applicable to winding deflection coils by hand since the preformed slots precisely position the wire and the hook members hold the end portion of the winding securely in posi tion.

FIG. 6A shows a skeleton view of the overall which produce of a coil as aforedescribed FIG. 6B shows how the winding segments in theslots b through j cooperate to form the overall coil pattern. Longitudinal portion 16 is the portion of each coil which lies in the slot along the axis of the core. Radial portion 15 represents the portion of the coils which are perpendicular to the axis of the core and which hook behind the hook members of the end caps. Transverse portions 17 are those parts of the windings that are designated by angle 0 and which produce no useful deflection component. Transverse portions 17 are maintained in a position perpendicular tothe axis of the yoke and outwardly displaced from portions 16 to avoid undesired end effects.

A yoke constructed according to the present invention will produce predictable magnetic fields with reduced spot focusing and distortion. v

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

What we claim is:

1. An electromagnetic deflection yoke for deflecting an electron beam, comprising:

a core portion;

first and second end caps, one of said end caps at each end of said core portion, wherein said end caps comprise a plurality of book members separated by a plurality of slots, said plurality of slots being aligned to form troughs along the axis of said core portion;

a plurality of windings for carrying electrical current, the longitudinal portions of said windings being placed in said plurality of slots for precise positioning of said longitudinal portions and end portions being held by said hook members to reduce defocusing and distortion.

2. An electromagnetic deflection yoke as in claim 1 wherein said core portion comprises magnetic core material formed with a plurality of longitudinal slots spaced around the inner perimeter of said magnetic core.

3. An electromagnetic deflection yoke as in claim 2 wherein said core portion has a cylindrical form.

4. An electromagnetic deflection yoke as in claim 1 wherein said core portion comprises a plurality of magnetic ring portions of a first character separated by a plurality of spacer ring portions of a different character to shape the magnetic flux pattern produced by said yoke.

5. An electromagnetic deflection yoke as in claim 1 wherein said core portion comprises a tapered magnetic core body;

said first end cap further comprises an extension which includes a plurality of troughs formed by slots along the inner surface of said extension, said extension being mounted on the inner perimeter of said magnetic core body.

6. An electromagnetic deflection yoke as in claim 1 wherein I ment;

a plurality of windings defining a coil, the longitudinal portions of said windings being located by said alignment means to extend along the inner surface of said core element,

and transverse winding retraining means on said core element, the end portions of said windings extending beyond said core element and being held in position by said retaining means.

8. An electromagnetic yoke as in claim 7, wherein said yoke is for use on a cathode-ray tube having a flaring bell portion, said core element being flared to fit said bell portion.

9. An electromagneticyoke as in claim 7 wherein said longitudinal winding alignment beams are uniformly spaced around the inner surface of said core element.

*;g;;g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,601,731 Dated August 2 1, 1971 Inventor) William R Christiana and Joseph F Hevesi It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, Line 26 delete which produce" and insert '-shape-.

Signed and sealed this Ltth day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GO'ITSCHALK Attesting Officer Commissioner of Patents 

1. An electromagnetic deflection yoke for deflecting an electron beam, comprising: a core portion; first and second end caps, one of said end caps at each end of said core portion, wherein said end caps comprise a plurality of hook members separated by a plurality of slots, said plurality of slots being aligned to form troughs along the axis of said core portion; a plurality of windings for carrying electrical current, the longitudinal portions of said windings being placed in said plurality of slots for precise positioning of said longitudinal portions and end portions being held by said hook members to reduce defocusing and distortion.
 2. An electromagnetic deflection yoke as in claim 1 wherein said core portion comprises magnetic core material formed with a plurality of longitudinal slots spaced around the inner perimeter of said magnetic core.
 3. An electromagnetic deflection yoke as in claim 2 wherein said core portion has a cylindrical form.
 4. An electromagnetic deflection yoke as in claim 1 wherein said core portion comprises a plurality of magnetic ring portions of a first character separated by a plurality of spacer ring portions of a different character to shape the magnetic flux pattern produced by said yoke.
 5. An electromagnetic deflection yoke as in claim 1 wherein said core portion comprises a tapered magnetic core body; said first end cap further comprises an extension which includes a plurality of troughs formed by slots along the inner surface of said extension, said extension being mounted on the inner perimeter of said magnetic core body.
 6. An electromagnetic deflection yoke as in claim 1 wherein each of said end caps contains a plurality of radially directed hook members spaced around the perimeter of said end caps shaped to define annular troughs operative to hold the end portions of said windings in a precise position outwardly displaced from said longitudinal portions of said windings.
 7. An electromagnetic yoke for use on a cathode-ray tube comprising: a core element; a longitudinal winding alignment means on said core element directed along the inner surface of said core element; a plurality of windings defining a coil, the longitudinal portions of said windings being located by said alignment means to extend along the inner surface of said core element, and transverse winding retraining means on said core element, the end portions of said windings extending beyond said core element and being held in position by said retaining means.
 8. An electromagnetic yoke as in claim 7, wherein said yoke is for use on a cathode-ray tube having a flaring bell portion, said core element being flared to fit said bell portion.
 9. An electromagnetic yoke as in claim 7 wherein said longitudinal winding alignment beams are uniformly spaced around the inner surface of said core element. 